This invention relates to a high-voltage variable resistor unit and a high-voltage electrical component.
A circuit board conventionally used for in a high-voltage variable resistor unit which is representative of a high-voltage electrical component is typically constructed in such a manner as shown in FIG. 8. A circuit board which is generally designated at a reference numeral 101 in FIG. 8 is adapted to be used for a conventional high-voltage variable resistor unit called a focusing pack which is constructed so as to variably output a focusing voltage and a screen voltage. The circuit board 101 is formed on a front surface thereof with a resistive pattern 102, which includes an input electrode E1, a focusing voltage output electrode E2, a screen voltage output electrode E3, a ground electrode E4, a first variable resistance element VR'1 for variation of a focusing voltage, a second variable resistance element VR'2 for variation of a screen voltage, and a fixed resistance element R' for voltage drop which is called a bleeder resistance. The resistive pattern 102 further includes connection patterns CP1 and CP2 acting as connection means which are contacted with a slide element (not shown) to electrically connect the slide element to the output electrodes E1 and E2, respectively. The slide element includes a slide contact slid on the variable resistance elements VR'1 and VR'2 and a contact pivotally moved on ends CP11 and CP21 of the connection patterns CP1 and CP2.
The high-voltage variable resistor unit has a size generally determined depending on an area of the circuit board 101, of which a size is determined depending on the resistive pattern 102. In determination of the resistive pattern, a distance between each adjacent two sections of the resistive pattern 102 is determined in view of so-called pattern dielectric strength for preventing generation of discharge which is generally set to be 1 mm/1 kV. Thus, distances A and B between the variable resistance elements VR'1, VR'2 and the ends CP11, CP21 of the connection patterns CP1, CP2 are likewise regulated by the pattern dielectric strength. This requires to increase a radius of a circular arc of each of the variable resistance elements VR'1 and VR'2 depending on a magnitude of a voltage applied thereto, resulting in a failure in down-sizing of the circuit board.